1. Field of the Invention
The present invention relates to a method of forming polycrystalline films, and more particularly to formation of polycrystalline films comprised essentially of cadmium sulfide.
2. Description of the Prior Art
Crystalline films of cadmium sulfide are useful in the formation of photovoltaic cells, among other uses. Prior art methods of forming polycrystalline films of cadmium sulfide typically utilize cadmium chloride as the cadmium salt constituent of the crystal forming solution. For example, in Jordan, et al., U.S. Pat. No. 3,880,633, a spray method for forming a cadmium sulfide photovoltaic cell is disclosed, utilizing a solution comprising cadmium chloride and thiourea.
Although it can be beneficial to utilize cadmium salts other than cadmium chloride in the formation of cadmium sulfide films, such as cadmium iodide, cadmium bromide, cadmium acetate, cadmium nitrate, etc., the prior art fails to teach a method whereby a uniform, continuous cadmium sulfide film can be formed utilizing such cadmium salts.
The present invention overcomes this difficulty. The method of the present invention teaches inclusion of a chlorine containing compound in the solution utilized to form the cadmium sulfide film to catalyze the film forming reaction. This method allows use of cadmium salts other than cadmium chloride.